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Amino Acids Degradation

Amino acids are the building blocks of proteins and therefore are a major component of our body. Those amino acids that are not needed as building blocks or that are damaged, need to undergo amino acid degradation and be recycled.

An amino acid consists of the amino group on the left, carboxylic acid group on the right and an R group that determines the identity of the amino acid. The primary purpose of the series of reactions described below is to take off the amino group from the amino acid so that its carbon skeleton can be used.

In the first step the amino group is transferred from the amino acid to alpha keto acid (alphaketoglutarate). This reaction is catalyzed by the enzymes called aminotransferases. The products of the first reaction are glutamate and the amino acid without the amine group. Some examples of the first reaction are :

alanine + alpha ketoglutarate -> glutamate + pyruvate

aspartate + alpha ketoglutarate -> glutamate + oxaloacetate

There reaction are reversible and thus can go both in the forward and reverse directions.

In the next reaction glutamate is turned into alphaketoglutarate with the help of glutamate dehydrogenase enzyme. In this reaction amino group is removed altogether, and is stores as ammonium in the mitochondria.